1. Field of Invention
The present invention relates to dispensers generally, and more specifically, to aerosol dispensers that are pressurized by mechanical energy instead of chemical energy.
2. Description of the Related Art
Aerosol dispensers have been in use for more than fifty years, and continue to gain in popularity because of the convenience of their use. However, many of those dispensers rely upon chemical propellants, including chloro-fluorocarbons and hydrocarbon compounds to pressurize the product. The use of chemical pressurizing agents creates special problems, including safety concerns in filling, shipping, handling, storing, using and disposing the pressurized, and often flammable containers. Another set of concerns involves questions relating to the effect of certain pressurizing chemical agents upon the earth""s ecosystem, including particular questions concerning their effect on the ozone layer, and questions concerning the effect of the release of volatile organic compounds into the atmosphere. Accordingly, there has been great interest in the development of aerosol dispensers that do not use chemical propellants, but which also retain the conveniences of use associated with the chemically charged dispensers.
Among the alternatives to chemically pressurized aerosol dispensers are various mechanically pressurized models using finger pumps and triggers. These typically require a continued vigorous pumping to produce a continuous spray, and, as a result, are inconvenient to use. Further, the duration of the spray is in most instances limited by (1) the length of the stroke of the pump or trigger, (2) the fact that the pressure of the spray in most instances does not remain constant during a discharge cycle but decreases rapidly near the end of the cycle with the spray becoming a wet stream or dribble, and (3) the fact that the device must generally be operated in an upright position. In addition, many of the finger-operated pumps are not capable of producing a fine mist or suitably atomized spray for use with such products as cosmetics and hair sprays. As a result, such devices only partially solve the problem of providing a convenient, yet safe alternative to chemically pressurized aerosol dispensers.
Other alternatives to chemically pressurized dispensers include various mechanically pressurized models that obtain prolonged spray time by storing a charge without the use of chemical propellants. Such xe2x80x9cstored chargexe2x80x9d dispensers include types that are mechanically pressurized at the point of assembly, as well as types that may be mechanically pressurized by an operator at the time of use.
Stored charge dispensers that are pressurized at the point of assembly often include a bladder that is pumped up with product. Examples include those described in U.S. Pat. Nos. 4,387,833 and 4,423,829.
Stored charge dispensers that are pressurized by an operator at the time of use typically include charging chambers that are charged by way of screw threads, cams, levers, ratchets, gears, and other constructions providing a mechanical advantage for pressurizing a product contained within a chamber. This type of dispenser will be referred to as a xe2x80x9ccharging chamber dispenser.xe2x80x9d Many ingenious charging dispensers have been produced. Examples include those described in U.S. Pat. No. 4,872,595 of Hammett et al., U.S. Pat. No. 4,222,500 of Capra et al., U.S. Pat. No. 4,174,052 of Capra et al., U.S. Pat. No. 4,167,941 of Capra et al., and U.S. Pat. No. 5,183,185 of Hutcheson et al., which is expressly incorporated by reference herein.
While some of the prior stored charge dispensers avoid some or all of the difficulties of the finger pump or trigger dispensers, the stored charge dispensers tend to have drawbacks of their own. In the devices pressurized at the point of assembly, the charging chamber is often an elastic bladder that remains charged during the life of the product, degrading over time, and these devices typically cannot be refilled with product. In the devices pressurized by an operator at the time of use, the charging chamber devices have been relatively difficult to manufacture due the large number of interrelated working parts required, and/or the fact that they are composed of parts not readily suited to high quantity, high yield injection molding production techniques, and/or the fact that they are required to be used with specially designed containers.
These drawbacks have tended to make the charging chamber dispensers expensive and not commercially feasible for mass market applications, and have tended to make other stored charge dispensers less than completely satisfactory substitutes for chemically pressurized dispensers. Accordingly, existing stored charge and charging chamber dispensers have only partially solved the problem of providing a convenient, yet safe alternative to chemically pressurized aerosol dispensers.
The current invention is a charging chamber dispenser that possesses specific improvements so that it combines convenience of use with commercial feasibility. It is believed that this is, finally, a non-chemical aerosol dispenser that retains the desirable features commonly associated with chemical aerosols, and is, therefore, a non-chemical aerosol dispenser that can attain widespread vendor and customer acceptance.
Accordingly, the mechanically pressurized aerosol dispensing system of this invention in one of the preferred embodiments consists essentially of: (a) a cap which houses a piston; (b) an actuator moveably attached to the cap, forming together with the cap a dispensing head assembly; and (c) an expandable elastic reservoir. The system is fitted over a standard container holding a liquid product, and includes a dip tube assembly to draw liquid into the dispensing head assembly, including an aerosol nozzle and valve, to release the contents out of the dispensing head assembly.
Complementary screw threads on the cap and actuator are selectively pitched so that a short twist of the threaded cap raises the piston, opening a charging chamber within the dispensing head assembly. This creates a vacuum with the resulting suction pulling the product up through the dip tube to fill the charging chamber. Twisting the cap in the opposite direction lowers the piston in a downstroke which closes the charging chamber, forcing the product into the expandable elastic reservoir. The reservoir expands under pressure, holding the product for subsequent discharge. Pushing a button, which is part of the standard valve assembly in the cap, releases the product through the nozzle.
The general working of the system briefly summarized above is enhanced by several specific improvements, including: (a) use of a snap-in piston so that the piston and the cap may be separately molded, allowing different materials for each and easier mold forms; (b) use of a container which is a separate piece from the dispensing head assembly, permitting easy filling of the container, and taking advantage of ordinary bottles and standard bottling technology; (c) use of a reservoir, piston and actuator in such a way as to realize the additional advantages of establishing a one-way valve mechanism for sealing the dip tube on the downstroke cycle, and also establishing a drain back mechanism for discharging undispensed product back into the container without the need of extra parts for either function, (d) use of a piston sealing mechanism which produces a tight seal while maintaining a low coefficient of friction so as to make the mechanical twisting motions of the cap and actuator easy, and (e) use of a flexible face fitment two-way valve mechanism for providing a positive shut off to reduce dribbling or seeping, while also preventing product build up behind the nozzle.
These and other specific improvements (and other embodiments) will be described in more detail later, and their significance will be explained. In summary, it is the cooperation of such elements as these in the system of this invention which results in a non-chemical aerosol that works from any position/orientation, even upside down, that does not require a finger pump to actuate, and that can be fitted to a wide variety of standard disposable or reusable containers. Further, the system of this invention produces a longer duration spray which does not become a wet stream or dribble near the end of the cycle, and a finely atomized high pressure spray which does not take inordinate mechanical force to charge. The system of this invention is simple and uses relatively few parts, all of which can be easily fabricated from existing materials and can be injection molded with existing mold techniques.
It is a specific objective of the system of this invention to solve substantially all of the problems that have, until now, prevented non-chemical aerosol dispensers from being widely accepted as the replacement for chemically pressurized aerosol dispensers.